1. Field of the Invention
The invention relates to a calibration device for the calibration of a tester channel of a tester device and to a tester system with such a calibration device.
2. Description of the Related Art
Semiconductor components are typically tested with the aid of test systems after their production. For this purpose, the semiconductor components, in the unsawn state, are contact-connected with the aid of a needle card having contact-connecting needles. The contact-connecting needles are connected via tester channels to a tester device which sends test signals to the connected integrated circuits and receives response signals from the integrated circuits via the tester channels. Usually, tester signals and response signals are transmitted via a tester channel, i.e., a single line between each integrated circuit and the tester device.
During testing, the temporal reference (timing) and the strength of signals are also taken into account besides the functionality. Since the tester channels essentially do not have the same electrical behavior with regard to the signal delay and the signal attenuation, it is necessary to calibrate the tester device. Each of the tester channels is provided with a delay element and an amplifying element in the tester device, in order that the test signals driven onto the tester channel are delayed in accordance with a variable time duration or, if appropriate, are accelerated, given an already preset delay, or amplified in accordance with a predetermined value. This makes it possible to ensure that the test signals are present at the integrated circuit with the same phase angle, i.e., with the same temporal reference with respect to a reference and with essentially the same signal strength. To set each delay unit and each amplifier unit of the tester channels, it is necessary to calibrate each tester channel.
The calibration of a tester channel is usually carried out by applying a calibration signal to a non-contact-connecting tester channel and measuring the temporal profile of the signal and the amplitude voltage of the resulting reflected calibration signal.
To achieve higher accuracies, a point-to-point calibration is used, particularly in test technology, at the component level. A calibration robot is usually used to adjust the properties of the tester channels. The calibration robot goes over the contact-connecting needles of the needle card individually and connects them to the measurement lines of the test. The tester channels are then individually adjusted with regard to the signal gain and the signal propagation time.
The technology of the dual transmission line is now increasingly being used in wafer test methods as well, with the result that the calibration robot can no longer be used. The substrate wafer on which the integrated circuits are situated is contact-connected to a needle card, which establish the contact between the integrated circuit and the tester device. The needle cards are usually mounted fixedly in the tester device and difficult to access externally, so that the calibration robot has no access to the needle card.
Therefore, in point-to-point calibration systems for dual transmission line systems, an additional electromechanically positionable calibration pad is provided in the tester device, which can be taken to the contact-connecting needle of the tester channel to be calibrated. The calibration pad contact-connects the contact-connecting needle of the needle card. This calibration device is complicated because a precise electromechanical positioning system is necessary. Moreover, the positionable calibration pad leaves adjacent contact-connecting needles at undefined potentials which can influence the calibration operation.